Structure and luminescent properties of luminous polypropylene fiber based on Sr2MgSi2OT：EU^2＋,Dy^3＋

The luminous polypropylene fiber based on long afterglow luminescent material Sr2MgSi2O7：Eu^2＋,Dy^3＋was prepared by melt-spinning process. Micro-morphology, phase composition, crystal structure, spectral features and afterglow properties of the lu-minescent fiber were tested and analyzed. The results indicated that the fiber had independent superposition phase features of both Sr2MgSi2O7：Eu2＋,Dy3＋and polypropylene. The range of its excitation wavelength was located between 250-450 nm;therefore, the luminescent fiber could be excited by ultraviolet or visible light. It could emit blue light of 460 nm wavelength after excitation, which was caused by the 5d-4f transition of Eu^2＋ions within the host lattice. The initial luminescent intensity was more than 0.8 cd/m^2, and afterglow life lasted 7 h. The afterglow decay was composed of rapid-decaying and slow-decaying processes, and the decay charac-teristics depended on the depth and concentration of trap level in the Sr2MgSi2O7：Eu^2＋,Dy^3＋.     

Preparation of Eu2+,Dy3+,Zr4+ ions co-doped strontium aluminate/molybdate multi-optical functional hybrid pigments for anti-counterfeiting

Eu²⁺,Dy³⁺ and Zr⁴⁺ ions co-doped strontium aluminate(i.e.,SrAl₂O₄:Eu²⁺,Dy³⁺,Zr⁴⁺)/molybdate(i.e.,Ho₂MoO₆ or Nd₂MoO₆) with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing.The phosphor and hybrid pigments were characterized by X-ray diffraction,scanning electron...     

Synthesis and luminescence properties of SrAleO4：Eue＋,Dy3＋ hollow microspheres via a solvothermal co-precipitation method

SrAl2O4:Eu2+,Dy3+ hollow microspheres were successfully prepared through a facile and mild solvothermal co-precipitation combining with a postcalcining process.The structure and particle morphology were investigated by X-ray diffraction(XRD),scanning and transmission electron microscopy(SEM and TEM)pictures,respectively.The mechanism for the formation of spherical SrAl2O4:Eu2+,Dy3+ phosphor was preliminary presented.After being irradiated with ultraviolet(UV)light,the spherical phosphor emitted long-lasting green phosphorescence.Both the photoluminescence(PL)spectra and luminance decay,compared with that of commercial bulky powders,revealed that the phosphors had efficient luminescent and long lasting properties.It was considered that the SrAl2O4:Eu2+,Dy3+ hollow microspheres had promising long-lasting phosphorescence with potential scale-dependent applications in photonic devices.     

Luminescence properties of composite material Sr2MgSi2O7:Eu2+,Dy3+/light conversion agent with multilayer structure

In order to improve the red luminescent properties,Sr₂ MgSi₂ O₇:Eu²⁺,Dy³⁺was selected as a blue persistent luminescent donor phosphor,while light conversion agent was utilized to tune the persistent luminescent spectra from blue to red.Composite red luminescent material Sr₂ MgSi₂ O₇:Eu²⁺,Dy³⁺/light conversion agent(SMED/LCA) was fabricated with light conversion agent and Sr₂ M...     

Preparation and characterization of flower-like SrAIeO4：Eu^2＋,Dy^3＋ phosphors by sol-gel process

A flower-like Eu²⁺ and Dy³⁺ co-doped SrAl₂O₄ long-lasting phosphorescent (LLP) phosphor was synthesized via the inorganic- salt-based sol-gel method. The crystal structure, morphology and optical properties of the composite were characterized. X-ray diffraction diffusion (XRD) data and DSC-TG curves of the phosphor revealed that the SrAl₂O₄ crystallites have been formed after the precursor was calcined at 900 °C and to be single-phase SrAl₂O₄ at 1100 °C. The SEM photographs indicated that the sample exhibited a universal flower-like morphology with crystallite size of about 1-2 μm. After being irradiated with ultraviolet (UV) light, the flower-like phosphor emitted long-lasting green phosphorescence with an excitation peak at 365 nm and emission peak at 500 nm which was ascribed to the characteristic 5d-4f transition of Eu²⁺. Both the PL spectra and the luminance decay curve revealed that this phosphor exhibited efficient luminescence and long lasting properties.     

Synthesis of Long Afterglow Phosphors Doped B SrAl2O4:Eu2+, Dy3+ and Its Luminescent Properties

The long afterglow luminescent material SrAl₂O₄: Eu²⁺, Dy³⁺ was prepared by high temperature solid-state method. Effects of doped B on the luminescent properties of phosphors SrAl₂O₄: Eu²⁺, Dy³⁺ were investigated by means of excitation spectra, emission spectra and X-ray diffraction analysis. As the result, the addition of H₃BO₃ as flux promotes the growth of crystalline and reduces the synthesizing temperature, but the wavelength of emission peak of photoluminescent material did not change with the variation of H₃BO₃ content. The effect of Dy³⁺ concentration on the luminescent properties of material was investigated. It was found that the luminescence of phosphors prepared under the condition of the amount of H₃BO₃ 5% and the mole ratio of Eu/Dy = 1/7(Eu = 0.02 mole) had better luminescent property and longer afterglow time.     

Investigation on luminescence properties of Ln^3＋ doped Sr3EuMgSi2O8 （Ln=Dy, Er, Ho）

The luminescent properties of Sr2.97MgSi2O8:Eu2+0.01 phosphors were investigated with different Ln3+0.02(Ln3+:Dy3+,Er3+,Ho3+) co-dopants. The co-dopants had no influence on both the structure of the lattice and the position of the emission peak. However, the afterglow properties of samples were enhanced with different co-dopants. The afterglow duration of the Dy3+ co-doped sample was longer than that of the others. Furthermore, the co-doping samples had stronger thermoluminescence (TL) intensity and therefore longer afterglow duration. At last, the self-reduction of Eu3+→Eu2+ was observed in an silicate compound of Sr3-xMgSi2O8:xEu phosphor in air condition. This is the first time to show a blue long afterglow phosphor synthesized avoiding reducing atmosphere.     

Ln3+ (Ln = Eu,Dy) - doped Sr2CeO4 fine phosphor particles: Wet chemical preparation,energy transfer and tunable luminescence

The Sr₂CeO₄:Ln³⁺ (Ln = Eu, Dy) fine phosphor particles were prepared by a facile wet chemical approach, in which the consecutive hydrothermal-combustion reaction was performed. The doping of Ln³⁺ into Sr₂CeO₄ has little influence on the structure of host, and the as-prepared samples display well-crystallized spherical or elliptical shape with an average particle size at about 100–200 nm. For Eu³⁺ ions-doped Sr₂CeO₄, with the increase of Eu³⁺-doping concentration, the blue light emission band with the maximum at 468 nm originating from a Ce⁴⁺ → O²⁻ charge transfer of the host decreases obviously and the characteristic red light emission of Eu³⁺ (⁵D₀→⁷F₂ transition at 618 nm) is enhanced gradually. Simultaneously, the fluorescent lifetime of the broadband emission of Sr₂CeO₄ decreases with the doping of Eu³⁺, indicating an efficient energy transfer from the host to the doping Eu³⁺ ions. The energy transfer efficiency from the host to Eu³⁺ was investigated in detail, and the emitting color of Sr₂CeO₄:Eu³⁺ can be easily tuned from blue to red by varying the doping concentration of Eu³⁺ ions. Moreover, the luminescence of Dy³⁺-doped Sr₂CeO₄ was also studied. Similar energy transfer phenomenon can be observed, and the incorporation of Dy³⁺ into Sr₂CeO₄ host leads to the characteristic emission of ⁴F_9/2 → ⁶H_15/2 (488 nm, blue light) and ⁴F_9/2 → ⁶H_13/2 (574 nm, yellow light) of Dy³⁺. The Sr₂CeO₄:Ln³⁺ fine particles with tunable luminescence are quite beneficial for its potential applications in the optoelectronic fields.     

Phase structure and temperature dependent luminescence properties of Sr2LiSiO4F: Eu2+ and Sr2MgSi2O7: Eu2+ phosphors

Green-emitting Sr2LiSiO4F:Eu2+ and blue-emitting Sr2MgSi2O7:Eu2+ phosphors were synthesized by the conventional high temperature solid-state route,respectively.Their structures and photoluminescenee properties were comparatively investigated.It was found that the mixture phases of Sr2MgSi2O7 and SrF2 were obtained when a part of Sr2+ in Sr2LiSiO4F was replaced by some amount of Mg2+ in order to design the possible SrMgLiSiO4F:Eu2+ phosphor.Based on the photoluminescence analysis,Sr2LiSiO4F:Eu2+ phosphor exhibited a green broad emission band of main peak at 513 nm under the excitation of 365 nm,while the Sr2MgSi2O7:Eu2+ and SrMgLiSiO4F:Eu2+ phosphor showed blue emission centered at 467 nm.The temperature dependent photoluminescence properties and room temperature decay time for the three kinds of phosphors were also discussed in this paper.     

Preparation and properties of rare earth luminous fiber containing red organic fluorescent pigment

Rare earth luminous fiber was prepared by method of melt spinning. X-ray diffraction （XRD）, scanning electron micros-copy （SEM）, and fluorescence spectrophotometer as well as afterglow brightness tester were used to characterize the resulting sam-ples. Results from XRD and SEM demonstrated that the phase of SrA12O4：Eu2＋,Dy3＋in the fiber was not destroyed in the manufac-turing process and the as-formed luminous fiber consisted of irregular particles. Under ultraviolet excitation, the luminous fiber exhib-ited a yellow-green and orange-red emission band with a maximum at 520 nm and around 600 nm originating from SrAl2O4：Eu2＋, Dy3＋and red organic fluorescent pigments. The energy transfer process was further studied. Furthermore, the emission colors of lu-minous fibers could be tuned from yellow-green to orange-red easily by doping red organic fluorescent pigment, making the materials have potential application in many areas.     

Single-phase white-emitting and tunable color phosphor Na3Sc2(PO4)3:Eu2+,Dy3+: Synthesis,luminescence and energy transfer

A series of Eu²⁺/Dy³⁺ single doped and co-doped Na₃Sc₂(PO₄)₃ phosphors were synthesized by the high-temperature solid-state method, and their phase, morphology, and luminescence properties were characterized. Under the excitation of 370 nm, the Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor can emit white light whose spectrum is composed of a broad emission band centered at 460 nm and the other three peaks at 483, 577, and 672 nm, respectively. There is energy transfer from Eu²⁺ to Dy³⁺ ion in Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor due to the good overlap between the emission spectrum of Na₃Sc₂(PO₄)₃:Eu²⁺ and the excitation spectrum of Na₃Sc₂(PO₄)₃:Dy³⁺, which is further confirmed by the fluorescence lifetime decrease of Eu²⁺ ion with the increase of Dy³⁺ concentration. The process of energy transfer is via dipole–quadruple interaction which is confirmed by applying Dexter's theory. By increasing the Dy³⁺ concentration, the color coordinates of the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors can be adjusted from blue to white, and then to yellow. The optimized concentration of Dy³⁺ ions is 4.0 mol%, beyond which the concentration quenching will take place. The Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor shows fairly good resistance to thermal quenching behavior, of which the emission intensity at 423 K can maintain 90.3% of the initial value (298 K). These results suggest that the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white LEDs.     

A single-phase full-color phosphor Sr2Ca2La(PO4)3O:Eu2+,Tb3+,Mn2+: Photoluminescence and energy transfer

A single-phase full-color emitting phosphor Sr₂Ca₂La(PO₄)₃O:Eu²⁺,Tb³⁺,Mn²⁺ was synthesized by the high temperature solid-state method. The phase formation, luminescence properties, thermal stability, and energy transfer from Eu²⁺ to Tb³⁺ and Eu²⁺ to Mn²⁺ in Sr₂Ca₂La(PO₄)₃O were investigated in details. Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu²⁺ to Tb³⁺ or Mn²⁺ ions by varying the ratio of Eu²⁺/Tb³⁺ or Eu²⁺/Mn²⁺ ions. White light was obtained with chromaticity coordinates of (0.3558, 0.3500) in the Sr₂Ca₂La(PO₄)₃O:0.04Eu²⁺,0.08Tb³⁺,0.40Mn²⁺ phosphor, suggesting their potential applications in white light emitting diodes.     

Enhanced afterglow performance of CaAl_2O_4:Eu~(2+),Nd~(3+) phosphors by co-doping Gd~(3+)

In order to effectively improve the afterglow properties of CaAl_2 O_4:Eu~(2+),Nd~(3+) phosphors,a series of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)(x=0,0.012,0.024,0.036,0.048,0.060 mol) phosphors were prepared by a high-temperature solid-phase approach.Crystalline composition and microstructure were characterized by XRD,TEM,HRTEM,and XPS,luminescence properties were systematically analyzed by fluorescence spectra,afterglow decay curves and TL glow curve.Results show that all of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)phosphors belong to monoclinic CaAl_2 O_4,without other cystalline phase.The blue emission at 442 nm is observed,which is assigned to the 4 f~65 d→4 f~7 transition of Eu~(2+) ions.Doping with appropriate amount of Gd~(3+) ions(x=0.036 mol) significantly improves the afterglow properties of phosphors,but the excessive doping of Gd~(3+) induces the fluorescent quenching.The doping of moderate Gd3+changes the traps states,the trap depth varies from 0.598 to 0.644 eV and the trap concentration is also greatly improved,thus significantly improving afterglow performance.     

Tunable luminescence in co-doped Zn3Al2Ge2O10:Cr3+ by controlling crystal field splitting and nephelauxetic effect

Ce³⁺/Dy³⁺/Tb³⁺/Eu³⁺/Mn²⁺and Cr³⁺ ions co-doped Zn₃ Al₂ Ge₂ O₁₀ phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn₃ Al₂ Ge2 O₁₀ phosphor,Emission,excitation spectra and decay curves confirm the tunable luminescence.Different degrees of the decrease of emission FWHM in Zn<...     

Luminescent ionic lattice occupation and wide tunable emission spectra of La2MgZrO6:Bi3+,Eu3+ double perovskite phosphors for white light LED

La₂Mg_1-x/2Zr_1-x/2O₆:xBi³⁺(x=0.01-0.035,abbreviated as LMZ:Bi³⁺) and La_2-yMg_0.99Zr_0.99O₆:0.02Bi³⁺,yEu³⁺(y=0.1-0.11,abbreviated as LMZ:Bi³⁺,Eu³⁺) double-perovskite phosphors were prepared through high-temperature solid-phase method.The emission spectrum of LMZ:xBi³⁺(x=0.01-0.035)phosphors excited at 353 nm is asymmetric in the range be...     

Long afterglow yellow luminescence from Pr3+ doped SrSc2O4

A yellow emitting long afterglow luminescence material SrSc₂O₄:Pr³⁺ was successfully prepared by solid state reaction method. SrSc₂O₄:Pr³⁺ phosphor shows a long afterglow luminescence peak at about 495, 545, 621, 630 and 657 nm, respectively, corresponding to the f–f transitions of Pr³⁺. The afterglow chromaticity coordinates of SrSc₂O₄:1 at%Pr³⁺ were calculated to be (0.35, 0.41), indicating that the afterglow emission is close to the light of yellow region. And, the afterglow luminescence of the optimal sample doped by 1 at%Pr³⁺ can persist for over 3 h. The thermoluminescence results suggest that there are three types of traps with depth of 0.61, 0.69 and 0.78 eV exiting for all the samples, which are produced by the addition of Pr³⁺ ions. The trap density of SrSc₂O₄:1 at%Pr³⁺ is the maximum when the incorporation of Pr³⁺ ions reaches 1 at%, which thus results in the longest afterglow luminescence. All the results indicate that SrSc₂O₄:Pr³⁺ can be a potential candidate of novel long afterglow phosphors.     

Eu2＋ and Dy3＋ codoped （Ca,Sr）7（SiO3）6Cl2 highly efficient yellow phosphor

Eu2+ and Dy3+ codoped(Ca,Sr)7(SiO3)6Cl2 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2+single-doped phosphor, while located at 548–544 nm for the Eu2+, Dy3+ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3+ was doped into the(Ca,Sr)7(SiO3)6Cl2:Eu2+ system. The composition-optimized sample with 3 mol.% of Dy3+ and constant 10 mol.% of Eu2+ exhibited a 220% PL enhancement compared to the phosphor with 10 mol.% Eu2+ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely(Ca,Sr)7(SiO3)6Cl2:3 mol.% Dy3+, 10 mol.% Eu2+ could get up to 24.6%. The synthesized yellow-emitting(Ca,Sr)7(SiO3)6Cl2:Dy3+,Eu2+ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.     

A novel long lasting phosphor Sr5 （PO4）3FxCll_x：Eu2＋,Gd3＋ prepared in air condition

A series of blue long afterglow mixed halide-phosphate phosphors Sr5 （PO4）3 FxCll-x：Eu2＋,Gd3＋ were synthesized in air by traditional solid-state reaction routte. The crystal structures, photoluminescence, thermolurninescenee properties and afterglow proper- ties of the phosphors were characterized systematically using X-ray diffraction （XRD）, luminescence spectrophotometer, microcom- puter thermoluminescence dosimeter and single photon counter, respectively. Under 280 nm excitation, the broadband emissions of Eu2＋ ions were observed at 445 nm （blue） due to the 4f7→4f65d transition. It was demonstrated that there existed the self-reduction of the Eu3＋ to Eu2＋ ions in this special halide-phosphate matrix in air condition. The addition of Gd3＋ ions obviously enhanced the after- glow properties of the single doped Eu2＋ ions in the halide-phosphate phosphors. And the content of the fluoride anions also had sig- nificant influence on the afterglow properties. All results indicated that Srs （PO4）3 FxCI1-x：Eu2＋,Gd3＋ might be potential phosphors for long lasting phosphorescence （LLP） materials.     

Plasmon-enhanced broad-band quantum-cutting of NaBaPO4:Eu2+,Er3+ phosphors with silver nano-particles

NaBaPO₄:Eu²⁺,Er³⁺ phosphors and Ag nano-particles (NPs) were prepared by the solid-state reaction and chemical reduction method, respectively. The fluorescence spectra and decay curves demonstrate the effective energy transfer from Eu²⁺ to Er³⁺ and the existence of three-photon quantum-cutting through two-step cross-relaxation of Er³⁺. The quantum-cutting emission is peaked at 1534 nm with a broad excitation band centered at 352 nm. Plasmon-enhanced quantum-cutting of NaBaPO₄:Eu²⁺,Er³⁺ phosphors was realized by decorating Ag NPs. The largest enhancement factor is 1.395. It is hopeful to improve the photovoltaic conversion efficiency of Ge solar cells by using this phosphor.     

Synthesis and characterization of needle-like BaAleO4：Eu,Dy phosphor via hydrothermal-homogeneous precipitation method

A needle-like Eu2+ and Dy3+ co-doped BaAl2O4 long-lasting phosphor was synthesized via a hydrothermal-homogeneous precipitation method assisted by cetyl trimethyl ammonium bromide(CTAB) as a template.The crystal structure,morphology and optical properties of the composites were characterized.XRD results showed that the single-phase BaAl2O4 was formed at 900 ℃ in an active carbon atmosphere,which was much lower than that prepared by traditional solid-state reaction method.Scanning electron microscopy(SEM) and transmission electron microscopy(TEM) observation revealed that the precursor had well-dispersed distribution and showed needle-like morphology with the average diameter of about 100 nm and the length up to 1 μm.The final product,BaAl2O4:Eu2+,Dy3+ phosphor,inherited the needle-like shape from precursor via adding the surfactant CTAB.After irradiation by ultraviolet radiation with 355 nm for 5 min,the phosphors emitted bluish green color long-lasting phosphorescence corresponding to the typical emission of Eu2+ ion.Both the photoluminescence spectra and luminance decay revealed that the phosphor had efficient luminescent and long-lasting properties.